1. Field of the Invention
The present invention relates to apparatus for the recognition of stylized characters formed on a document, and has particular application in apparatus for processing information at high speed.
2. Description of the Prior Art
When processing documents used in commercial transactions, inventory control and general business operations, reliance is made to a great extent on documents such as checks, bills of sale, receipts, invoices, tags or other documents containing information in the form of stylized characters. That is to say, characters of the human language which are conformed in such a way as to be easily identified by associated character recognition apparatus capable of generating sequences of electric signals specific to the form of the characters. These stylized characters can be constituted, for example, by well known symbols which have been established in accordance with the requirement of the American Association of Banks and which are now currently designated under the name of characters E13B.
To identify these stylized characters, utilization may be made of character recognition apparatus of the type described in French patent No. 1,248,226 in which a variable voltage signal generated during the passage of a stylized character before a transducing reading head is divided into a certain number of partial signals, the partial signals are then simultaneously applied to several correlation rings, each of which is associated with a respective one of the characters to be identified. A correlation ring associated with the character to be read delivers an output voltage which is greater than the output voltages of the other correlation rings. By comparison of the voltages delivered by the different correlation rings, it is then possible to identify the character read.
Such character recognition apparatus, however, has certain disadvantages. For example, it is not always possible to identify the character read accurately because of the fact that the documents which carry the stylized characters are not always themselves perfect, and have defects such as surface irregularities or undesirable particles may be encrusted in the document during its manufacture or handling. Ink marks can be formed involuntarily on the document during printing of the characters. Defaults can also occur during printing and cause incompletely formed characters. All of these defects cause, in general, an alteration of form of the wave generated by the transducing head during the reading of a character, so that output voltages having practically the same maximum value may appear simultaneously at the outputs of two or several correlation rings. These multiple maximum voltages are then interpreted as an error and lead to the rejection of the document.
To compensate for these disadvantages, character recognition apparatus has been proposed as described and shown in French Patent No. 1,483,115. In this patent, the method of character recognition is based on the determination of the total energy content of signals corresponding to each form of wave, the determination of the energy content of these signals in the regions of precise frequency and the comparison of the energy content of these signals. Since, in this apparatus, a comparison is made between the energy at different frequencies and the total energy contained in the character, and comparisons are thus based on relative values and not absolute values, this method of recognition is not affected by parasites. However, in such apparatus, the number of precise frequency regions which serve for the comparison, as well as their size, is difficult to determine with accuracy. This determination is obtained, most often, only at the end of multiple trials undertaken during the adjustment of this apparatus. Thus, while the structure of each of the elements making up this apparatus is relatively simple, the realization of such apparatus is extensive, delicate and particularly costly.
Another form of character recognition is described and shown in French Patent No. 1,420,769. In this patent, each stylized character is considered to be constituted of a succession of portions of a character resulting from the cutting of this character into several parallel bands along a direction perpendicular to the direction of exploration of the reading head. The signal engendered during reading of this character is formed of a sequence of analogous elementary signals corresponding each to a respective one of the portions of this character. The recognition apparatus which is described in this patent comprises a generator of correlation signals, multiplying apparatus in which each elementary signal is multiplied by a correlation signal engendered by this generator, integrating apparatus which integrates the product delivered by this multiplying apparatus, classification apparatus which, in response to each integral received, delivers one of three values +1, -1 or 0, in accordance with the slope of the elementary signal corresponding to this integral, and an identification block which further comprises logic blocks based on types of characters to be read and which receive from the classification apparatus groups of values +1, -1 or 0 engendered consecutively by the reading of a character and furnish an identification signal at the output of the logic block which is associated with this character. Such recognition apparatus suffers from the disadvantage of requiring a large number of analogous circuits since the method of recognition rests on the determination of the slope of the various elementary signals resulting from the reading of a character. Further, this recognition apparatus requires a number of control elements and command elements both for assuring the indispensable synchronization between the different elementary signals and the correlation signals as well as for effecting the classification of the diverse integrals furnished by the integrating apparatus. Finally, this recognition apparatus is not protected from disturbances which are consecutively produced by an excess ink or a defect of inking and which effecting the form of the wave created by the reading head and more particularly the slope of the various elementary signals picking up this form of wave, result almost always in a rejection of the document.